Resin composition, molded article, multilayered pipe and method for producing the same

ABSTRACT

An object of the present invention is to provide a multilayered pipe having a layer comprising a resin composition containing EVOH, which is unlikely to exhibit the occurrence of cracking in the EVOH layer due to oxidative degeneration and has excellent gas barrier property even during long-term usage at high temperatures, and also to provide a resin composition for obtaining the multilayered pipe. The present invention relates to a resin composition containing 0.001 to 5 parts by mass of an antioxidant (B) and 0.00001 to 0.3 parts by mass of a conjugated polyene compound (C) having a molecular weight of 1000 or less, relative to 100 parts by mass of an ethylene-vinyl alcohol copolymer (A).

TECHNICAL FIELD

The present invention relates to a resin composition, a molded articlehaving a layer comprising the resin composition, and a multilayeredpipe. Furthermore, the present invention relates to a method forproducing the molded article and the multilayered pipe.

BACKGROUND ART

Conventionally, a metallic pipe for hot water circulation is usedprimarily in floor heating by the hot water circulation method. Whenlaying such a pipe for hot water circulation, the pipe is embeddedinside concrete and installed under the floor in most cases, and themaintenance and repair becomes extremely difficult once the pipe hasbeen installed. Furthermore, the pipe is normally required to have along-term durability of about 50 years. Based on such severe conditions,a use of a plastic pipe that is cheaper than a metallic pipe and alsodoes not involve corrosion of the pipe material is desired.Polyethylene, polypropylene, polybutene, etc., are used as the plasticpipe materials.

However, when such a plastic pipe is used in a floor heating systembased on the hot water circulation method, there is a problem ofcorrosion of the metallic parts of heat exchanger, pump and the like,due to oxygen. A possible reason of this corrosion is that the oxygenpresent in the atmosphere passes through the plastic walls, andpenetrates and dissolves in the hot water circulating within the pipe.Thus, a multilayer polyethylene pipe having aluminum as the intermediatelayer is used, but due to cracking of the aluminum layer possibly due tothe change in temperature, this multilayered pipe cannot preventcorrosion due to the oxygen.

As a solution to this problem, various multilayered pipes including aplastic resin having excellent oxygen gas barrier property andpolyethylene are evaluated. Among these, a multilayered pipe using anethylene-vinyl alcohol copolymer (hereinafter, may be abbreviated asEVOH) is confirmed to have the highest oxygen barrier property and mostexcellent mechanical strength, and these days, EVOH multilayer plasticpipes are used widely as pipes for hot water circulation. For example, ahot water circulation pipe including an EVOH layer as the intermediatelayer (see Patent document 1: JP 61-140691 A and a hot water circulationpipe having an EVOH layer as the outermost layer (see Patent document 2:JP 02-74341 A are known.

However, in the case of a hot water circulation pipe, the exposure ofthe EVOH layer to remarkably high temperatures for a long period of timegradually accelerates oxidation degradation of EVOH due to the oxygenpresent in the air. Although the oxygen barrier property of EVOH is notseriously affected by a small amount of degradation, the mechanicalstrength may decline due to oxidation degradation giving rise to cracksparallel to the lengthwise direction of the EVOH layer. When crackingthus occurs as a result of aging degradation, the excellent oxygenbarrier property of EVOH is obviously lost, and with these cracks as thestarting point, fissures running through the pipe walls might occur. Insuch a case, the water in the pipe leaks out under the floor causing abig problem.

The addition of an antioxidant is effective against the oxidationdegradation of EVOH in the air, and a composition containing EVOH and anamide having a hindered phenol group (see Patent document 3: JP63-286459 A) as well as a composition in which an aliphatic carboxylicacid containing three to nine carbon atoms and a hindered phenolantioxidant are mixed with EVOH (see Patent document 4: JP 4-227744 A)are known. By making use of these techniques, it becomes possible toextend the life of the hot water circulation pipe to a large extent.

However, in the recent resource-saving and energy-saving trend, where alarge increase in the lifespan of household equipment is demanded, thelifespan of the hot water circulation pipes is also desired to be muchmore.

Furthermore, until now, floor heating by the hot water circulationmethod is mainly prevalent in western countries such as Northern Europe,but in the recent years, this heating system is gradually beginning togain popularity in Japan as well. In Japanese houses, there are manyrestrictions in the floor area for laying down hot water circulationpipes, and in many cases the pipes have to be installed with a smallbending radius. Therefore, when secondary processing is performed tobend the pipe, cracking occurs easily in a direction perpendicular tothe lengthwise direction of the EVOH layer. Further improvements arenecessary even with regard to cracking due to the distortion during suchsecondary processing.

Furthermore, an insulated multilayered pipe including an inner pipecarrying gas or liquid, an insulation foam layer covering the innerpipe, and an outer pipe covering the insulation foam layer is used as apipe for district energy (area-wide air conditioning) (see Patentdocument 5: EP 0634602 A1). Conventionally, the insulation foam layer issurrounded by a foil (film) adhering on to the outer pipe. Examples ofthe foil include metals such as aluminum, and polyethylene from theviewpoint of a thermoformable material. However, the conventionally usedaluminum foil is difficult to handle, and on the other hand, thepolyethylene film fails to provide long-term insulation effect withoutproper permeation prevention of carbon dioxide, pentane, andcyclopentane used in the blowing agent of the insulation foam.Therefore, the use of a multilayered pipe including EVOH having gasbarrier property as an outer pipe is being examined from the viewpointof improvement in handling and permeation prevention of carbon dioxide,pentane, and cyclopentane (see Patent document 6: EP 1355103 A1).However, even the insulated multilayered pipe has a problem ofacceleration of oxidation degradation of EVOH due to the oxygen in theair during long-term usage. When the mechanical strength declines andcracks occur parallel to the lengthwise direction of the EVOH layer as aresult of oxidation degradation, blowing gas is dispersed from theinsulated multilayered pipe and the insulation performance declines. Inorder to solve such a problem, the EVOH layer is desired to have a longlife.

On the other hand, it is disclosed that by using an EVOH resincomposition (not a blended composition with polyolefin) containing aconjugated polyene compound having a boiling point of 20° C. or more inEVOH, a molded article with less coloring and less formation of agel-type object during molding is obtained (see Patent document 7: JP9-71620 A), but the patent document does not examine the decline in themechanical strength due to oxidation degradation at high temperatures.

PRIOR ART DOCUMENTS Patent Documents

-   Patent document 1: JP 61-140691 A-   Patent document 2: JP 2-74341 A-   Patent document 3: JP 63-286459 A-   Patent document 4: JP 4-227744 A-   Patent document 5: EP 0634602 A1-   Patent document 6: EP 1355103 A1-   Patent document 7: JP 9-71620 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

An object of the present invention is to provide a molded article and amultilayered pipe having a layer including a resin compositioncontaining EVOH, which cause less crack in the EVOH layer due tooxidation degradation and have excellent gas barrier property evenduring long-term usage at high temperatures, and also to provide a resincomposition for obtaining the molded article and the multilayered pipe.

Means for Solving the Problems

The above problem can be solved by providing a resin compositioncontaining 0.001 to 5 parts by mass of an antioxidant (B) and 0.00001 to0.3 parts by mass of a conjugated polyene compound (C) having amolecular weight of 1000 or less, relative to 100 parts by mass of anethylene-vinyl alcohol copolymer (A).

The content of the conjugated polyene compound (C) is preferably 0.00005to 0.2 parts by mass, and more preferably 0.0001 to 0.15 parts by mass.Furthermore, the conjugated polyene compound (C) is preferably at leastone type selected from the group consisting of sorbic acid, sorbic acidsalt, and myrcene, and more preferably sorbic acid and/or its salt.

The content of the antioxidant (B) is preferably 0.01 to 4 parts bymass. Furthermore, the antioxidant (B) is preferably a compound having ahindered amine group and/or a compound having a hindered phenol group.

A molded article and a multilayered pipe having a layer including theresin composition are also suitable embodiments of the presentinvention. In the multilayered pipe, the layer including the resincomposition is desired to be the outermost layer.

Furthermore, a hot water circulation pipe including the multilayeredpipe is also a suitable embodiment of the present invention. Aninsulated multilayered pipe formed by including an insulation foam layerin the multilayered pipe is also a suitable embodiment of the presentinvention. Such an insulated multilayered pipe is desired to have alayer including an inner pipe, an insulation foam layer, and a layerincluding the resin composition, in a sequence from the inner side.

Furthermore, it is preferred that the method for producing the moldedarticle and the multilayered pipe includes a step of cooling by usingwater having a temperature of 10 to 70° C. immediately after molding.

Effect of the Invention

According to the resin composition of the present invention, it ispossible to provide a multilayered pipe having a layer including theresin composition containing EVOH, which cause less crack in the EVOHlayer due to oxidation degradation and has excellent appearance and gasbarrier property even during long-term usage at high temperatures.

MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be explained in the orderof the resin composition and the method for producing the same, and themolded article and multilayered pipe and the method for producing thesame.

[Resin Composition]

The resin composition of the present invention contains anethylene-vinyl alcohol copolymer (EVOH) (A), an antioxidant (B), and aconjugated polyene compound (C) having a molecular weight of 1000 orless.

(EVOH (A))

EVOH (A) is a copolymer having an ethylene unit and a vinyl alcohol unitas the main structural units. Normally, the EVOH is obtained bycopolymerizing ethylene and vinyl ester, and then saponifying theresulting ethylene-vinyl ester copolymer. Particularly, that obtained bysaponifying an ethylene-vinyl acetate copolymer is typical.

When the ethylene unit content of the EVOH (A) (that is, the ratio ofthe number of ethylene units per total number of monomer units in theEVOH) becomes too high, the gas barrier property tends to decline. Onthe other hand, because the oxidation degradation of the EVOH (A) occurswith the hydroxyl group of the vinyl alcohol units as the base point,oxidation degradation occurs easily when the ethylene unit content islow (the content of the vinyl alcohol units is high). From thisviewpoint, the ethylene unit content is desired to be 10 to 65 mol %,with 15 to 60 mol % being more preferable, and 20 to 50 mol % beingparticularly preferable.

When the degree of saponification of the EVOH (A) (that is, the ratio ofthe number of vinyl alcohol units per total number of vinyl alcoholunits and vinyl ester units in the EVOH) is low, the gas barrierproperty might deteriorate, and the elimination reaction of carboxylicacid occurs easily under high temperatures. From this viewpoint, thedegree of saponification is preferably 96 mol % or more, and morepreferably 99 mol % or more. EVOH with a degree of saponification of 99mol % or more makes it possible to achieve a multilayered pipe withexcellent gas barrier property, and is particularly preferred in thepresent invention.

The EVOH (A) may also include another polymerizable monomer unit to theextent that does not inhibit the effect of the present invention,usually in the range of not 5 mol % or less. Examples of thepolymerizable monomer include α-olefins such as propylene, 1-butene,1-hexene, and 4-methyl-1-pentene; (metha)acrylic acid esters;unsaturated carboxylic acids such as maleic acid, fumaric acid, anditaconic acid; alkyl vinyl ethers; N-(2-dimethylaminoethyl)methacrylamide or its quaternary compounds, N-vinylimidazole or itsquaternary compounds, N-vinylpyrrolidone, N,N-butoxymethylacrylamide,vinyltrimethoxysilane, vinylmethyldimethoxysilane,vinyldimethylmethoxysilane, and the like.

The melt index (MI; measured at 190° C., under a load of 2160 g) of theEVOH (A) is not particularly limited, and preferably is in the range of0.1 to 100 g/10 minutes, more preferably is 0.5 to 50 g/10 minutes, andparticularly preferably is 1.0 to 30 g/10 minutes. By setting the meltindex of the EVOH (A) in the above-mentioned range, the melt formabilityof the resin composition thus obtained can be improved, and amultilayered pipe with excellent appearance can be obtained. EVOH havinga melt point close to or exceeding 190° C. is measured under a load of2160 g and at a plurality of temperatures above the melt point, and thereciprocal of the absolute temperature is plotted on the horizontal axiswhile the logarithm of MFR is plotted on the vertical axis of a semiloggraph, and the MFR is expressed by values extrapolated at 190° C.

(Antioxidant (B))

The antioxidant (B) is a compound having antioxidant capacity. Althoughthe melt point of the antioxidant (B) is not necessarily limited, it isdesired to be 170° C. or less. If the melt point of the antioxidant (B)exceeds 170° C., when a resin composition is produced by melt blending,the antioxidant (B) may localize in the resin composition because itdoesn't melt in an extruder, and the high-concentration portions in theresin composition may be colored.

The molecular weight of the antioxidant (B) is preferably 300 or more.When the molecular weight is below 300, the antioxidant might bleed outon the surface of the molded article and the multilayered pipe that areobtained, possibly resulting in poor appearance of the molded articleand the multilayered pipe, and the thermal stability of the resincomposition also declines easily. The molecular weight is preferably 400or more, and particularly preferable is 500 or more. On the other hand,the upper limit of the molecular weight of the antioxidant (B) is notparticularly limited, but from the viewpoint of dispersibility, 8,000 orless is preferable, 6,000 or less is more preferable, and 4,000 or lessis particularly preferable.

A compound having a hindered phenol group is suitable to be used as theantioxidant (B). While on one hand a compound having a hindered phenolgroup has excellent thermal stability, it also has the ability tocapture the oxygen radical that is the cause of oxidation degradation,and when blended with the resin composition as an antioxidant, thecompound exhibits an excellent effect of preventing oxidationdegradation.

Commercially available products, for example those described below, canbe used as the compound having a hindered phenol group.

(1) “IRGANOX 1010” manufactured by BASF: Pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] with a meltpoint in the range of 110 to 125° C. and a molecular weight of 1178(2) “IRGANOX 1076” manufactured by BASF:Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate with a meltpoint in the range of 50 to 55° C. and a molecular weight of 531(3) “IRGANOX 1098” manufactured by BASF:N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide)]with a melt point in the range of 156 to 161° C. and a molecular weightof 637(4) “IRGANOX 245” manufactured by BASF: Triethyleneglycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] with amelt point in the range of 76 to 79° C. and a molecular weight of 587(5) “IRGANOX 259” manufactured by BASF:1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] witha melt point in the range of 104 to 108° C. and a molecular weight of639(6) “Sumilizer MDP-s” manufactured by Sumitomo Chemical Co., Ltd.:2,2′-methylene-bis(4-methyl-6-tert-butylphenol) with a melt point ofabout 128° C. and a molecular weight of 341(7) “Sumilizer GM” manufactured by Sumitomo Chemical Co., Ltd.:2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-meth ylphenylacrylate with a melt point of about 128° C. and a molecular weight of395(8) “Sumilizer GA-80” manufactured by Sumitomo Chemical Co., Ltd.:3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecanewith a melt point of about 110° C. and a molecular weight of 741

A compound having a hindered amine group is also suitable to be used asthe antioxidant (B). When a compound having a hindered amine group isblended with the resin composition as the antioxidant (B), the compounddoes not just prevent heat degradation of EVOH, but also exhibits theeffect of capturing the aldehyde generated as a result of thermaldecomposition of EVOH, and can inhibit generation of a void or airbubble during molding by reducing generation of decomposition gases.Furthermore, when the resin composition of the present invention is usedas a food packaging container, the problem of spoiling of the taste ofthe content due to the smell of the aldehyde is solved because of thecapture of the aldehyde.

A piperidine derivative is preferably used as the compound having ahindered amine group, and particularly, a 2,2,6,6-tetraalkyl piperidinederivative having a substituent group at the fourth position ispreferable. A carboxyl group, an alkoxy group, or an alkylamino groupcan be used as the substituent at the fourth position.

Furthermore, an alkyl group may be substituted at the N-position of thehindered amine group, but the use of the compound having a hinderedamine group, where a hydrogen atom is bonded at the N-position ispreferable due to an excellent heat stabilizing effect.

Commercially available products, for example those described below, canbe used as the compound having a hindered amine group.

(9) “TINUVIN 770” manufactured by BASF:Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate with a melt point in therange of 81 to 85° C. and a molecular weight of 481 (10) “TINUVIN 765”manufactured by BASF: Bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate,which is a liquid compound with a molecular weight of 509, and1,2,2,6,6-pentamethyl-4-piperidyl sebacate (mixture)(11) “TINUVIN 622LD” manufactured by BASF: Polycondensate of dimethylsuccinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidinewith a melt point in the range of 55 to 70° C. and a molecular weight of3100 to 4000(12) “CHIMASSORB 119FL” manufactured by BASF: Condensate ofN,N′-bis(3-aminopropyl)ethylenediamine and2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazinewith a melt point in the range of 130 to 140° C. and a molecular weightof 2000 or more(13) “CHIMASSORB 944LD” manufactured by BASF:poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazin-2,4-diyl](2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene(2,2,6,6-tetramethyl-4-piperidyl)imino]] with a melt point in the rangeof 100 to 135° C. and a molecular weight between 2000 and 3100(14) “TINUVIN 144” manufactured by BASF: Bis(i,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate witha melt point in the range of 146 to 150° C. and a molecular weight of685(15) “UVINUL 4050H” manufactured by BASF: N,N′-1,6-hexanediylbis{N-(2,2,6,6-tetramethyl-4-piperidinyl)formamide} with a melt point of157° C. and a molecular weight of 450(16) “UVINUL 5050H” manufactured by BASF: Compound having the followingstructure with a melt point in the range of 104 to 112° C. and amolecular weight of about 3500

Such compounds having a hindered phenol group or a hindered amine groupmay be used either individually, or by combining two or more types.

The content of the antioxidant (B) is 0.001 to 5 parts by mass, relativeto 100 parts by mass of the EVOH (A). If the content of the antioxidant(B) is less than 0.001 parts by mass, the effect of the presentinvention might not be achieved. On the other hand, if the content ismore than 5 parts by mass, there might be improper dispersion of theantioxidant (B) and due to which the appearance of the molded articleand multilayered pipe might deteriorate easily. The content of theantioxidant (B) is preferably between 0.01 and 4 parts by mass, and morepreferably between 0.1 and 3 parts by mass relative to 100 parts by massof the EVOH (A).

(Conjugated Polyene Compound (C))

Conjugated polyene compounds (C) are compounds having so-calledconjugated double bonds, which have a structure in which carbon-carbondouble bonds and carbon-carbon single bonds are connected alternately,with the number of carbon-carbon double bonds being two or more. Aconjugated polyene compound may be a conjugated diene having twocarbon-carbon double bonds and one carbon-carbon single bond connectedalternately, or a conjugated triene having three carbon-carbon doublebonds and two carbon-carbon single bonds connected alternately, or maybe a conjugated polyene compound having a greater number ofcarbon-carbon double bonds and carbon-carbon single bonds connectedalternately. Polyene compounds having seven or fewer carbon-carbondouble bonds to conjugate are preferred because if the number ofcarbon-carbon double bonds to conjugate is eight or more, the conjugatedpolyene compound may color the molded article or the multilayered pipeby its own color. Also, the conjugated polyene compound may contain, inone molecule, a plurality of independent sets of conjugated double bondsconsisting of two or more carbon-carbon double bonds, wherein the setsare not conjugated to each other, each. For example, a compound such aswood oil that has three conjugated trienes in one molecule can beincluded in conjugated polyene compounds (C) of the present invention.Furthermore, in addition to conjugated double bonds, the conjugatedpolyene compounds may also contain other functional groups such ascarboxylic group and its salt, hydroxyl group, ester group, carbonylgroup, ether group, amino group, imino group, amide group, cyano group,diazo group, nitro group, sulfone group and its salt, sulfonyl group,sulfoxide group, sulfide group, thiol group, phosphate group and itssalt, phenyl group, halogen atom, double bond, and triple bond.

The molecular weight of the conjugated polyene compound (C) must be 1000or less. If the molecular weight is more than 1000, the dispersion stateof the conjugated polyene compound (C) in EVOH worsens, and theappearance of the molded article and multilayered pipe aftermelt-forming deteriorates. The molecular weight is preferably 500 orless, and more preferably 300 or less.

Specific examples of conjugated polyene compounds (C) include conjugateddiene compounds having conjugated structures of two carbon-carbon doublebonds such as: isoprene; 2,3-dimethyl-1,3-butadiene;2,3-diethyl-1,3-butadiene; 2-t-butyl-1,3-butadiene; 1,3-pentadiene;2,3-dimethyl-1,3-pentadiene; 2,4-dimethyl-1,3-pentadiene;3,4-dimethyl-1,3-pentadiene; 3-ethyl-1,3-pentadiene; 2-methyl-1,3-pentadiene; 3-methyl-1,3-pentadiene; 4-methyl-1,3-pentadiene;1,3-hexadiene; 2,4-hexadiene; 2,5-dimethyl-2,4-hexadiene; 1,3-octadiene;1,3-cyclopentadiene; 1,3-cyclohexadiene; 1-phenyl-1,3-butadiene;1,4-diphenyl-1,3-butadiene; 1-methoxy-1,3-butadiene;2-methoxy-1,3-butadiene; 1-ethoxy-1,3-butadiene; 2-ethoxy-1,3-butadiene;2-nitro-1,3-butadiene; chloroprene; 1-chloro-1,3-butadiene;1-bromo-1,3-butadiene; 2-bromo-1,3-butadiene; fulvene; tropone; ocimene;phellandrene; myrcene; farnesene; cembrene; sorbic acid; sorbic acidester; sorbic acid salt; and abietic acid; conjugated triene compoundshaving conjugated structures of three carbon-carbon double bonds suchas: 1,3,5-hexatriene; 2,4,6-octatriene-1-carboxylic acid; eleostearicacid; wood oil; and cholecalciferol; and conjugated polyene compoundshaving conjugated structures of four or more carbon-carbon double bondssuch as: cyclooctatetraene; 2,4,6,8-decatetraene-1-carboxylic acid;retinol; and retinoic acid. Two or more types of polyene compounds canalso be used together.

Among these, sorbic acid, sorbic acid ester, sorbic acid salt, andmyrcene such as β-myrcene and their mixtures are preferable, andparticularly, sorbic acid, sorbic acid salt and their mixtures arewidely used industrially as food additives, and preferable from theviewpoint of hygiene and availability, and also suitable because oftheir effectiveness in preventing oxidative degeneration at hightemperatures.

The content of the conjugated polyene compound (C) is 0.00001 to 0.3parts by mass, relative to 100 parts by mass of the EVOH (A). If thecontent of the conjugated polyene compound (C) is less than 0.00001parts by mass, the effect of the present invention is not fullyachieved. On the other hand, if the content is more than 0.3 parts bymass, the gelation of the resin composition is accelerated due to whichthe appearance of the molded article and multilayered pipe mightdeteriorate easily. The content of the conjugated polyene compound (C)is preferably 0.00005 to 0.2 parts by mass, more preferably 0.0001 to0.15 parts by mass, and particularly preferably 0.001 to 0.1 parts bymass, relative to 100 parts by mass of the EVOH (A).

(Phosphoric Acid Compound (D))

If a phosphoric acid compound (D) is blended with the resin compositionof the present invention, the oxidation degradation of EVOH under hightemperatures is prevented, and the occurrence of cracking due tooxidation degradation can be reduced, and therefore, the blending of aphosphoric acid compound is preferable.

The phosphoric acid compound (D) is not particularly restricted, forexample, various types of acids such as phosphoric acid and phosphorousacid, and their salts can be used. The phosphate may be included in anyform such as primary phosphate, secondary phosphate, and tertiaryphosphate. And its cation type is also not particularly restricted,which is preferably an alkali metal salt or alkaline-earth-metal salt.Among these, the phosphoric acid compound is preferably added asphosphoric acid, sodium dihydrogen phosphate, potassium dihydrogenphosphate, disodium hydrogen phosphate, and dipotassium hydrogenphosphate, and is more preferably added as phosphoric acid, sodiumdihydrogen phosphate, and potassium dihydrogen phosphate.

The content of the phosphoric acid compound (D) is preferably between0.0001 and 0.03 parts by mass, in terms of phosphate radical, relativeto 100 parts by mass of the EVOH (A). If the content of the phosphoricacid compound (D) is less than 0.0001, the effect of addition of thephosphoric acid compound (D) is not fully achieved. On the other hand,if the content is more than 0.03 parts by mass, it might lead to theformation of gel during melt forming. The content of the phosphoric acidcompound (D) is preferably between 0.0003 and 0.025 parts by mass, andmore preferably between 0.0005 and 0.02 parts by mass, relative to 100parts by mass of the EVOH (A).

(Boron Compound (E))

If a boron compound (E) is blended with the resin composition of thepresent invention, the oxidation degradation of EVOH under hightemperatures is prevented, and the occurrence of cracking due tooxidation degradation can be reduced, and therefore, the blending of aboron compound is preferable.

The boron compound (E) is not particularly restricted, and includes forexample, boric acids such as orthoboric acid, metaboric acid, andtetraboric acid; boric acid esters such as triethyl borate and trimethylborate; borates such as alkali metal salt and alkali earth-metal salt ofeach of the above-mentioned boric acids, and borax; and boron hydrides.Among these compounds, orthoboric acid is preferable.

The content of the boron compound (E) is preferably between 0.002 and0.2 parts by mass, in terms of boron element, relative to 100 parts bymass of the EVOH (A). If the content of the boron compound (E) is lessthan 0.002 parts by mass, the effect of addition of the boron compound(E) might not be fully achieved. On the other hand, if the content ismore than 0.2 parts by mass, the performance of melt-forming mightdeteriorate. The content of the boron compound (E) is preferably between0.005 and 0.1 parts by mass, relative to 100 parts by mass of the EVOH(A).

(Lubricant)

The addition of a lubricant to the resin composition of the presentinvention is also preferable because it is effective in reducing theoccurrence of cracking due to oxidative degeneration. Higher fattyacids, such as lauric acid, myristic acid, palmitic acid, stearic acid,behenic acid, and oleic acid; higher fatty acid metal salts such asaluminum salt, calcium salt, zinc salt, magnesium salt, and barium saltof each of the above higher fatty acids; higher fatty acid esters, suchas methyl ester, isopropyl ester, butyl ester, and octyl ester of eachof the above higher fatty acids; higher fatty acid amides such assaturated fatty acid amides like stearic acid amide and behenic amide,unsaturated fatty acid amides like oleic acid amide and erucic acidamide, and higher fatty acid amides like ethylene bis stearic acidamide, ethylene bis oleic acid amide, ethylene bis erucic acid amide,and ethylene bis lauric acid amide; low-molecular weight polyolefinssuch as low molecular weight polyethylene or low molecular weightpolypropylene having a number average molecular weight of about 500 toabout 10,000, or an acid-modified product thereof; higher alcohols;ester oligomers; and fluoride ethylene resins may be used as thelubricant. And preferably higher fatty acids and/or their metal salts,esters, and amides, and more preferably higher fatty acid metal saltsand/or higher fatty acid amides may be used. Two or more types of theselubricants may also be used in combination.

The content of the lubricants is preferably between 0.00001 and 1 partby mass relative to 100 parts by mass of the EVOH (A). If the content ofthe lubricants is below 0.00001 parts by mass, sufficient effect ofprevention of cracking due to oxidation degradation may not be obtained.On the other hand, if the content is more than 1 part by mass, thelubricants are separated at the time of melt-forming the resincomposition, and as a result, various abnormalities may arise. Thecontent of the lubricants is preferably between 0.00005 and 0.5 parts bymass relative to 100 parts by mass of EVOH (A).

(Other Additives)

The resin composition of the present invention may also include variousadditives such as ultraviolet absorbers, plasticizers, antistaticagents, coloring agents, and fillers, and at the same time, otherpolymer compounds may be blended in proper amount to the extent they donot inhibit the effect of the present invention.

Specific examples of additives are shown below.

Ultraviolet absorbers: Ethylene-2-cyano-3,3′-diphenyl acrylate,2-(2′-hydroxyl-5′-methylphenyl)benzotriazole,2-(2′-hydroxyl-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-hydroxyl-4-methoxybenzophenone-2,2′-dihydroxyl-4-methoxybenzophenone,2-hydroxyl-4-octoxybenzophenone, and the like.

Plasticizers: Dimethyl phthalate, diethyl phthalate, dioctyl phthalate,wax, liquid paraffin, phosphoric acid esters, and the like.Antistatic agents: Pentaerythritol monostearate, sorbitan monopalmitate,sulfated polyolefins, polyethylene oxide, carbowax, and the like.Coloring agents: Titanium oxide, carbon black, phthalocyanine,quinacridone, indolin, azo pigments, colcothar, and the like.Fillers: Glass fiber, asbestos, balastonite, calcium silicate, and thelike.

Furthermore, in order to improve various properties such as thermalstability at the time of melt-forming of the EVOH (A), additives such asorganic acids like acetic acid and lactic acid, and inorganic acidsother than the phosphoric acid compounds and boron compounds describedabove, or metal salts of these acids formed with elements of periodictable Groups I, II and III may be added in the pellet of the EVOH (A)within the reasonable extent that does not inhibit the effect of thepresent invention.

[Method for Producing the Resin Composition]

There are no particular restrictions with respect to methods for uniformblending of the EVOH (A), the antioxidant (B), and the conjugatedpolyene compound (C) to obtain the resin composition according to thepresent invention. A method wherein the three constituents, that is, theEVOH (A), the antioxidant (B), and the conjugated polyene compound (C)are dry-blended together and then melt-blended; a method wherein theantioxidant (B) or the conjugated polyene compound (C) is blended inadvance in the EVOH (A) to prepare pellets, and the obtained pellets aredry-blended with the remaining components and then melt-blended; and amethod wherein the antioxidant (B) and/or the conjugated polyenecompound (C) are blended with a part of the EVOH (A) at a highconcentration to prepare a granulated master batch, which is dry-blendedwith the remaining components and then melt-blended can be listed asexamples.

Among these, the preferable method is the one wherein the conjugatedpolyene compound (C) is blended in advance in the EVOH (A) to preparepellets, and the obtained pellets are dry-blended with the antioxidant(B) and then melt-blended. This method enables uniform blending of eachcomponent. Furthermore, the method wherein the conjugated polyenecompound (C) is blended in advance in the EVOH (A) to prepare pellets,the antioxidant (B) is blended in the pellets at high concentration toprepare a master batch, and the master batch is dry-blended with thepellets in which the antioxidant (B) is not blended and thenmelt-blended is also preferable because of improved dispersibility ofthe antioxidant (B).

In the aforementioned method, in order to obtain the pellet by blendingthe conjugated polyene compound (C) in the EVOH (A), the EVOH (A) isdissolved in a good solvent such as water/methanol mixed solvent, and aconjugated polyene compound (C) is dissolved in this solution. The mixedsolution is extruded into a poor solvent through a nozzle, etc. Thedeposit is precipitated and/or solidified, then rinsed and/or dried toobtain the pellet. This method is particularly preferable because thedispersibility of the conjugated polyene compound (C) that is notdispersed easily in a uniform manner in the EVOH (A) with a smallblending amount is improved.

There are no particular restrictions with respect to the mixing toolsfor each constituent to obtain the resin composition of the presentinvention, for example, ribbon blenders, high-speed mixer-cokneaders,mixing rolls, extruders, intensive mixers, or the like, can be listed.

[Molded Article]

The resin composition of the present invention can be molded intodesired molded articles such as films, sheets, tubes, bottles, cups, andpipes through publicly known melt extruders, compression moldingmachines, transfer molding machines, injection molding machines, blowmolding machines, heat molding machines, rotary molding machines,dipping molding machines, and the like. The extrusion temperature formolding is generally in the range of 170 to 350° C., although it issuitably selected depending on the type of the resin used, molecularweight, blending ratio of the composition, or the type of moldingmachine and the like.

A preferable embodiment of the molded article obtained from the resincomposition of the present invention is a multilayered structure havingat least one layer including the resin composition of the presentinvention. The layer structure of the multilayered structure is notparticularly restricted, and if the layer obtained from the resincomposition of the present invention is represented by “E”, the layerobtained from an adhesive resin is represented by “Ad”, and the layerobtained from a thermoplastic resin is represented by “T”, the followinglayer configurations can be exemplified. A polyolef in modified by anunsaturated carboxylic acid or its derivative is preferably used as theadhesive resin. Furthermore, thermoplastic resins include polyolef inssuch as polyethylene, polypropylene, poly 1-butene, and poly4-methyl-1-pentene, and among these, polyethylene, and particularly,high-density polyethylene is preferable.

2 layers Ad/E 3 layers T/Ad/E, Ad/E/Ad, E/Ad/E 4 layers T/Ad/E/Ad,Ad/E/Ad/E 5 layers E/Ad/T/Ad/E, T/Ad/E/Ad/T, Ad/E/Ad/E/Ad, T/Ad/E/Ad/E 6layers T/Ad/E/Ad/E/Ad 7 layers T/Ad/E/Ad/E/Ad/T

Furthermore, in such a multilayered structure, the thermoplastic resinand/or the adhesive resin can also be substituted by scrap of themultilayered structure. The scrap of other polyolefin molded articlescan also be mixed and used.

The method of producing the multilayered structure is not particularlyrestricted. For example, the method of melt-extruding the thermoplasticresin on the molded article (such as a film or sheet) obtained from theresin composition of the present invention, the method of co-extrudingthe resin composition of the present invention with anotherthermoplastic resin, the method of coinjecting the resin composition andthe thermoplastic resin of the present invention, or the method oflaminating the molded article obtained from the resin composition of thepresent invention with a film or sheet of another material by using awell-known adhesive such as an organic titanium compound, an isocyanatecompound, and a polyester compound, can be used.

[Multilayered Pipe]

The multilayered pipe of the present invention has a layer including theaforementioned resin composition. In the multilayered pipe of thepresent invention, the aforementioned resin composition is primarilycomposed of the EVOH (A), which exhibits excellent gas barrier property,and because the oxidation degradation of the EVOH (A) under hightemperatures is inhibited, cracking does not occur easily as a result ofoxidation degradation in the layer including the aforementioned resincomposition (EVOH layer) even when used under high temperatures for longperiods of time. By making use of this characteristic, the multilayeredpipe of the present invention is preferably used as a hot watercirculation pipe and an insulated multilayered pipe for district energy.

The layer configuration of the aforementioned multilayered structure canbe adopted as the layer configuration of the multilayered pipe. When themultilayered pipe is used as a hot water circulation pipe, thethree-layer configuration of T/Ad/E in which the layer including theaforementioned resin composition is the outermost layer is generallyadopted. This is because in reality many pipe manufacturers are makinguse of this configuration since by adding equipment for co-extrusioncoating of the resin composition of the present invention and theadhesive resin to the manufacturing line of single-layer pipes, such asthe existing crosslinked polyolefins, the manufacturing line can beeasily converted to the manufacturing line for the multilayered pipe ofthe present invention.

By providing a polyolef in layer or the like on both sides of the layerincluding the resin composition of the present invention, and using theresin composition layer as the intermediate layer, scratching of theresin composition layer can be prevented effectively. However, when themultilayered pipe is used as a hot water circulation pipe, such as afloor heating pipe, the risk of the layer including the resincomposition of the present invention getting scratched or damaged due tophysical impact is relatively small because the pipe is normallyembedded under the floor. In fact, from the viewpoint of the gas barrierproperty, the arrangement of the resin composition layer as theoutermost layer is desired. The gas barrier property of the EVOH (A)shows a large humidity dependence, and because the barrier propertiesdecline under high-humidity conditions, if the layer including the resincomposition of the present invention is arranged as the outermost layer,the layer including the resin composition of the present inventioncomposed primarily of the EVOH (A) is positioned at the farthestlocation from the inner surface of the pipe that is in contact withwater, which makes it the most advantageous layer configuration from theviewpoint of the barrier performance of the multilayered pipe. On theother hand, when the EVOH layer is arranged as the outermost layer, thislayer comes in direct contact with the air, and generally oxidationdegradation of the EVOH layer easily occurs. Under such environmentalconditions, by arranging the layer including the resin composition ofthe present invention, which is not easily affected by oxidationdegradation even under high temperatures, as the outermost layer, theeffect of the present invention of providing a multilayered pipe whichhas improved barrier properties and can reduce occurrence of crackingdue to oxidation degradation, is exhibited effectively.

Furthermore, when the multilayered pipe of the present invention is usedas an insulated multilayered pipe for district energy, etc., thethree-layer configuration of T/Ad/E (hereinafter, may be abbreviated aslaminate 1) in which the layer including the aforementioned resincomposition is arranged inwards from the thermoplastic resin layer, orthe five-layer configuration of T/Ad/E/Ad/T (hereinafter, may beabbreviated as laminate 2) configured from the viewpoint of preventingscratching of the resin composition layer are preferable.

The configuration of the insulated multilayered pipe for districtenergy, etc. is not particularly restricted, for example, the pipe ispreferably arranged in the order of an inner pipe, an insulation foamlayer covering the surrounding of the inner pipe, and the aforementionedlaminate 1 or 2 having a layer including the resin composition of thepresent invention as the outer layer, from the inner side.

The type (material), shape, and size of the pipe used as the inner pipeis not particularly restricted as long as a heat carrier such as gas andliquid can be transferred, and they can be selected appropriatelydepending on the type of the heat carrier, and the purpose and form ofusage of the pipe. Specifically, metals such as steel, stainless, andaluminum; polyolefins (such as polyethylene, crosslinked polyethylene(PEX), polypropylene, poly 1-butene, and poly 4-methyl-1-pentene), andthe aforementioned laminate 1 or 2 having a layer including the resincomposition of the present invention can be listed as examples, andamong these, crosslinked polyethylene (PEX) is preferably used.

Polyurethane foam, polyethylene foam, polystyrene foam, phenol foam, andpolyisocyanurate foam can be used as the insulation foam, and from theviewpoint of improvement in the insulation performance, polyurethanefoam is preferably used.

Freon gas, various freon gas alternatives, water, chlorinatedhydrocarbons, hydrocarbons, and carbon dioxide can be used as theblowing agent of insulation foam, but from the viewpoint of the foamingeffect and the impact on the environment, hydrocarbons, particularly,n-pentane and cyclopentane are preferably used.

The methods for producing the insulated multilayered pipe include, forexample, inserting the inner pipe used to transfer the heat carrierinside the pipe-shaped outer layer, fixing the inner pipe with a spacerto form a double pipe, and then pouring various foam feedstocks in thespace between the inner pipe and the outer layer to result in foam andhardening. The material of the aforementioned spacer is not particularlyrestricted, however in order to reduce the damage caused to the innerpipe and the outer layer by the spacer, polyethylene or polyurethane isdesired.

[Method for Producing the Molded Article and Multilayered Pipe]

The method for producing the multilayered pipe is explained below, but apart or all of the producing method can also be applied to other moldedarticles (such as films and sheets).

The multilayered pipe of the present invention can be produced byperforming co-extrusion coating of the resin composition of the presentinvention and the adhesive resin on a single-layer pipe such as thecrosslinked polyolefin as above described. When performing co-extrusioncoating of the resin composition of the present invention and theadhesive resin on the single-layer pipe, a film of melted resincomposition of the present invention and adhesive resin can simply becoated on the single-layer pipe, however, the adhesive power between thepipe and the coating may be insufficient, which could cause the coatingto tear when used for a long period of time, resulting in loss of thegas barrier property. As a measure, performing flame treatment and/orcorona discharge treatment on the surface of the pipe to be coated,before the coating process, can prove to be effective.

Another method of multilayer formation for producing a multilayered pipeincludes the so-called co-extrusion molding method. In this method, anumber of extruders corresponding to the number of types of resin layersare used, and resins melted in each extruder are simultaneously extrudedto form a laminated layer structure. Another method of multilayerformation, such as dry lamination, can also be applied.

The method for producing the multilayered pipe preferably includes astep of cooling immediately after molding, by using water having atemperature of 10 to 70° C. That is, it is desired that aftermelt-forming, the resin composition layer of the present invention issolidified by cooling using water having a temperature of 10 to 70° C.before the solidification of the resin composition layer. If thetemperature of the cooling water is too low, then in the succeedingsecondary processing process wherein the multilayered pipe is bent,cracking occurs easily due to distortion in the layer including theresin composition of the present invention at the bent part. Althoughthe details of the cause of the occurrence of cracking due to distortionare not clear, the residual stress in the molded article is expected toplay a role. From this viewpoint, the temperature of the cooling wateris preferably 15° C. or more, and more preferably 20° C. or more. On theother hand, even if the temperature of the cooling water is too high,then during the secondary processing process, cracking occurs easily dueto distortion in the layer including the resin composition of thepresent invention in the bent part. The details of the cause are againnot very clear, but this could possibly be due to too high a degree ofcrystallization of the layer including the resin composition of thepresent invention. From this viewpoint, the temperature of the coolingwater is preferably 60° C. or less, and more preferably 50° C. or less.

By performing secondary processing of the multilayered pipe obtained bythe aforementioned method, various molded articles can be obtained. Themethod of secondary processing is not particularly restricted, and anappropriate well-known method of secondary processing can be selected.For example, a method containing heating the multilayered pipe at 80 to160° C. and changing it in to the desired shape, and then fixing theshape of the pipe for one minute to two hours to solidify, may beapplied.

EXAMPLES

Next, the present invention will be explained in greater detail throughexamples, however, the present invention is not limited to theseexamples. In the following producing example, the content of eachconstituent was quantitatively determined by the below method.

(1) Conjugated Polyene Compound

Dried EVOH pellets were frozen and crushed, and sifted through a100-mesh sieve to eliminate coarse particles. A 10 g portion of thepowder obtained was submitted to Soxhlet extraction for 48 hours with100 ml of chloroform. The amount of conjugated polyene compound in theextraction liquid was determined by quantitative analysis through highperformance liquid chromatography. The quantitative determination wasmade using calibration curves prepared with the reference standard ofeach conjugated polyene compound.

(2) Phosphoric Acid Compound and Boron Compound

Dried EVOH pellets were crushed by freezing and crushing. In 0.5 gportion of the powder obtained, 5 ml of nitric acid was added, and thenwet degradation was performed using “Speedwave MWS-2” manufactured byBERGHOF. The liquid obtained after wet degradation was diluted withion-exchanged water to obtain a total solution of 50 ml. Quantitativedetermination of elemental phosphorus and boron element in the dilutedsolution was performed using an ICP emission spectrochemical analysisdevice “Optima 4300 DV” manufactured by PerkinElmer Japan Co., Ltd. Theamount of the phosphoric acid compound was calculated as a value interms of phosphate radical, and the amount of the boron compound wascalculated as a value in terms of boron element. An analytical curveprepared from commercially-available standard solution was used for thequantitative determination of both compounds.

Producing Example 1 Produce of EVOH Pellets (1)

2 kg of EVOH resin having an ethylene unit content of 32 mol %, having adegree of saponification of 99.8 mol %, and limiting viscosity[η]ph of0.112 L/g as measured by using a liquid mixture of water/phenol=15/85(mass ratio) as a solvent, was added to 18 kg of a mixed solvent ofwater/methanol=40/60 (mass ratio) and completely dissolved by stirringfor six hours at 60° C. To this solution, 1 g of sorbic acid (0.05 partsby mass relative to 100 parts by mass of EVOH) was added as a conjugatedpolyene compound and completely dissolved by stirring for one additionalhour to obtain an EVOH solution containing sorbic acid. This solutionwas continuously extruded into a coagulation bath ofwater/methanol=90/10 (mass ratio) with temperature adjusted to 0° C.through a nozzle of 4 mm diameter to coagulate EVOH in a strand shape.This strand was then introduced into a pelletizer to obtain porous EVOHchips.

The porous EVOH chips thus obtained were rinsed with an acetic acidaqueous solution and ion-exchanged water followed by immersion in anaqueous solution containing acetic acid, potassium dihydrogen phosphate,and sodium acetate. EVOH chips were isolated from the aqueous solutionused for processing, dewatered, and then, dried for 4 hours in a hot-airdrier at 80° C., followed by drying for 16 hours at 100° C. to obtaindried EVOH pellets (1). The content of the phosphorous compound in theEVOH pellets (1) was 100 ppm, in terms of phosphate radical. The meltindex (ASTM-D1238, measured at 190° C., under a load of 2160 g) of theEVOH pellets (1) was 1.6 g/10 minutes.

Producing Example 2 Produce of EVOH Pellets (2)

EVOH pellets (2) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.01 g of sorbicacid (0.0005 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound in the EVOH pellets (2) was 100 ppm,in terms of phosphate radical, and the melt index (ASTM-D1238, measuredat 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 3 Produce of EVOH Pellets (3)

EVOH pellets (3) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.2 g of sorbicacid (0.01 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound of the EVOH pellets (3) was 100 ppm,in terms of phosphate radical, and the melt index (ASTM-D1238, measuredat 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 4 Produce of EVOH Pellets (4)

EVOH pellets (4) were obtained in the same manner as in ProducingExample 1 except for the use of β-myrcene as the conjugated polyenecompound instead of the sorbic acid in the Producing Example 1. Thecontent of the phosphorous compound in the EVOH pellets (4) was 100 ppm,in terms of phosphate radical, and the melt index (ASTM-D1238, measuredat 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 5 Produce of EVOH Pellets (5)

EVOH pellets (5) were obtained in the same manner as in ProducingExample 1 except for the use of potassium sorbate as the conjugatedpolyene compound instead of the sorbic acid in the Producing Example 1.The content of the phosphorous compound in the EVOH pellets (5) was 100ppm, in terms of phosphate radical, and the melt index (ASTM-D1238,measured at 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 6 Produce of EVOH Pellets (6)

Porous EVOH chips were obtained in the same manner as in ProducingExample 1 except that EVOH resin having an ethylene unit content of 32mol %, having a degree of saponification of 99.8 mol %, and limitingviscosity[η]ph of 0.092 L/g as measured by using a liquid mixture ofwater/phenol=15/85 (mass ratio) as a solvent, was used as the EVOHresin. The porous EVOH chips thus obtained were rinsed with an aceticacid aqueous solution and ion-exchanged water followed by immersion inan aqueous solution containing acetic acid, potassium dihydrogenphosphate, sodium acetate, and boric acid. EVOH chips were isolated fromthe aqueous solution used for processing, dewatered, and then, dried for4 hours in a hot-air drier at 80° C., followed by drying for 16 hours at100° C. to obtain dried EVOH pellets (6). The content of the phosphorouscompound in the EVOH pellets (6) was 100 ppm, in terms of phosphateradical, and the content of the boron compound was 170 ppm in terms ofboron element. The melt index (ASTM-D1238, measured at 190° C., under aload of 2160 g) was 1.6 g/10 minutes.

Producing Example 7 Produce of EVOH Pellets (7)

EVOH pellets (7) were obtained in the same manner as in ProducingExample 1 except that potassium dihydrogen phosphate was not added tothe aqueous solution used for immersion, when immersing the EVOH chips.The content of the phosphorous compound in the EVOH pellets (7) was 0ppm and the melt index (ASTM-D1238, measured at 190° C., under a load of2160 g) was 1.6 g/10 minutes.

Producing Example 8 Produce of EVOH Pellets (8)

EVOH pellets (8) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 6 g of sorbic acid(0.3 parts by mass relative to 100 parts by mass of EVOH). The contentof the phosphorous compound in the EVOH pellets (8) was 100 ppm, interms of phosphate radical, and the melt index (ASTM-D1238, measured at190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 9 Produce of EVOH Pellets (9)

EVOH pellets (9) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.0002 g of sorbicacid (0.00001 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound in the EVOH pellets (9) was 100 ppm,in terms of phosphate radical, and the melt index (ASTM-D1238, measuredat 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 10 Produce of EVOH Pellets (10)

EVOH pellets (10) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.001 g of sorbicacid (0.00005 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound in the EVOH pellets (10) was 100ppm, in terms of phosphate radical, and the melt index (ASTM-D1238,measured at 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 11 Produce of EVOH Pellets (11)

EVOH pellets (11) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.002 g of sorbicacid (0.0001 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound in the EVOH pellets (11) was 100ppm, in terms of phosphate radical, and the melt index (ASTM-D1238,measured at 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 12 Produce of EVOH Pellets (12)

EVOH pellets (12) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 2 g of sorbic acid(0.1 parts by mass relative to 100 parts by mass of EVOH). The contentof the phosphorous compound in the EVOH pellets (12) was 100 ppm, interms of phosphate radical, and the melt index (ASTM-D1238, measured at190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 13 Produce of EVOH Pellets (13)

EVOH pellets (13) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 0.02 g of sorbicacid (0.001 parts by mass relative to 100 parts by mass of EVOH). Thecontent of the phosphorous compound in the EVOH pellets (13) was 100ppm, in terms of phosphate radical, and the melt index (ASTM-D1238,measured at 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 14 Produce of EVOH Pellets (14)

EVOH pellets (14) were obtained in the same manner as in ProducingExample 1 except that the conjugated polyene compound was not blended.The content of the phosphorous compound in the EVOH pellets (14) was 100ppm, in terms of phosphate radical, and the melt index (ASTM-D1238,measured at 190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Producing Example 15 Produce of EVOH Pellets (15)

EVOH pellets (15) were obtained in the same manner as in ProducingExample 1 except for the use of a blending amount of 10 g of sorbic acid(0.5 parts by mass relative to 100 parts by mass of EVOH). The contentof the phosphorous compound in the EVOH pellets (15) was 100 ppm, interms of phosphate radical, and the melt index (ASTM-D1238, measured at190° C., under a load of 2160 g) was 1.6 g/10 minutes.

Example 1

0.5 parts by mass ofN,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide]was dry-blended into the EVOH pellets (1), as the antioxidant, relativeto 100 parts by mass of EVOH and the resulting mixture was pelletizedafter blending at an extrusion temperature of 200° C. by using a twinscrew co-rotating extruder of 30 mm φ(TEX-30N, manufactured by JapanSteel Works, Ltd.) to obtain resin composition pellets.

The resin composition pellets thus obtained were used to produce asingle-layer film under the below-mentioned conditions by using anextruder having a diameter of 20 mm (“D2020” manufactured by Toyo SeikiSeisaku-Sho, Ltd.”, D (mm)=20, L/D=20, compression ratio=2.0, screw:full flight).

Extrusion temperature: Supply unit/Compression unit/Meteringunit/Die=175/210/220/220° C.

Screw rotation speed: 90 rpm

Output rate: 2.1 kg/hr

Take-up roll temperature: 80° C.

Take-up roll speed: 0.9 m/minute

Film thickness: 100 μm

Examples 2 to 19, Comparative Examples 1 to 5

Pellets of the resin composition according to these examples andcomparative examples, as well as a single-layer film formed therewithwas obtained in the same manner as in Example 1 except that the types ofEVOH pellets and antioxidants, and the blending amount of theantioxidant described in Table 1 were used.

(Method of Evaluating the Single-Layer Film)

The single-layer film obtained in Examples 1 to 19 and ComparativeExamples 1 to 5 was evaluated by the following method. The evaluationresults are shown in Table 1 along with the type and ratio of eachconstituent.

(1) Resistance to Oxidative Degeneration

The aging variation of the tensile strength of the single-layer filmthus obtained was evaluated by measuring a plurality of samples withdifferent heat treatment periods under the below evaluation conditions.The time period when the elongation at break becomes ¼ of the sample inwhich heat treatment is not performed was found out and set as the indexof resistance to oxidative degeneration.

Evaluation Conditions:

Heat treatment: Extracted after performing heat treatment for apredetermined time period inside a hot-air drier set at 140° C.

Humidification conditions: Immersed for five days in water having atemperature of 20° C., wiped off the surface water, and kept aside fortwo weeks in a room with 20° C. and 65% RH.

Measurement of tensile strength: Sample width 15 mm, Chuck interval 30mm, Tension speed 50 mm/minute, measurement atmosphere 20° C. to 65% RH

In the above evaluation, because the deterioration in the gas barrierproperty of the EVOH layer as a result of occurrence of cracking due tooxidative degeneration becomes remarkable when the elongation at breakbecomes ¼ or less, this time period until when the elongation at breakbecomes ¼ can be assumed as one of the indexes of lifespan based on theoxidative degeneration of EVOH under high temperatures. The time perioduntil when the elongation at break becomes ¼ shows an Arrhenius typetemperature dependence, and if the time period (lifespan) until when theelongation at break becomes ¼ at 80° C. is assumed as 100 years or more,the time period until when the elongation at break becomes ¼ at 140° C.must be set as 210 hours or more.

(2) Appearance

The existence of flowing spots, streaks, and fish eye in thesingle-layer film thus obtained was checked visually. The appearance ofthe single-layer film was judged based on the following standards:

A: There are no flowing spots and streaks, and fish eyes either do notexist or exist in very small number.

B: There are a few flowing spots and streaks, and fish eyes exist in asmall number.

C: Flowing spots and streaks are remarkably present, and there are alarge number of fish eyes.

TABLE 1 (B) Antioxidant (C) Conjugated polyene (D) Phosphoric (E) BoronBlending compound acid compound compound Resistance to amount*² BlendingBlending Blending oxidative Types of EVOH (Part by amount*² amount*³amount*⁴ degeneration pellets Types*¹ mass) Types (ppm) (ppm) (ppm) (hr)Appearance Example 1 EVOH pellet (1) antioxidant (1) 0.5 sorbic acid 500100 0 276 A Example 2 EVOH pellet (2) antioxidant (1) 0.5 sorbic acid 5100 0 230 A Example 3 EVOH pellet (3) antioxidant (1) 0.5 sorbic acid100 100 0 245 A Example 4 EVOH pellet (1) antioxidant (2) 0.2 sorbicacid 500 100 0 248 A Example 5 EVOH pellet (4) antioxidant (1) 0.5β-myrcene 500 100 0 251 A Example 6 EVOH pellet (5) antioxidant (1) 0.5potassium 500 100 0 260 A sorbate Example 7 EVOH pellet (6) antioxidant(1) 0.5 sorbic acid 500 100 170 302 A Example 8 EVOH pellet (7)antioxidant (1) 0.5 sorbic acid 500 0 0 239 A Example 9 EVOH pellet (1)antioxidant (1) 5 sorbic acid 500 100 0 304 B Example 10 EVOH pellet (1)antioxidant (1) 0.001 sorbic acid 500 100 0 213 A Example 11 EVOH pellet(1) antioxidant (1) 0.01 sorbic acid 500 100 0 228 A Example 12 EVOHpellet (1) antioxidant (1) 3 sorbic acid 500 100 0 281 A Example 13 EVOHpellet (1) antioxidant (1) 0.1 sorbic acid 500 100 0 239 A Example 14EVOH pellet (8) antioxidant (1) 0.5 sorbic acid 3000 100 0 312 B Example15 EVOH pellet (9) antioxidant (1) 0.5 sorbic acid 0.1 100 0 210 AExample 16 EVOH pellet (10) antioxidant (1) 0.5 sorbic acid 0.5 100 0215 A Example 17 EVOH pellet (11) antioxidant (1) 0.5 sorbic acid 1 1000 223 A Example 18 EVOH pellet (12) antioxidant (1) 0.5 sorbic acid 1000100 0 284 A Example 19 EVOH pellet (13) antioxidant (1) 0.5 sorbic acid10 100 0 241 A Comparative EVOH pellet (14) NA 0 NA 0 100 0 74 A Example1 Comparative EVOH pellet (14) antioxidant (1) 0.5 NA 0 100 0 199 AExample 2 Comparative EVOH pellet (1) NA 0 sorbic acid 500 100 0 89 AExample 3 Comparative EVOH pellet (1) antioxidant (1) 10 sorbic acid 500100 0 —*⁵ —*⁶ Example 4 Comparative EVOH pellet (15) antioxidant (1) 0.5sorbic acid 5000 100 0 —*⁵ C Example 5 *¹Antioxidant (1) . . .N,N′-hexane-1,6-diylbis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide] Antioxidant (2) . . . N,N′-1,6-hexanediylbis[N-(2,2,6,6-tetramethyl-4-piperidinyl) formamide] *²Blending amountrelative to 100 parts by mass of EVOH *³Value in terms of phosphateradical *⁴Value in terms of boron element *⁵Not measured *⁶Impossible toform film

Example 20

100 parts by mass of a high-density polyethylene (“Yukaron Hard BX-50”manufactured by Mitsubishi Chemical Corporation having a density of0.952 g/cc and an MFR of 0.5 g/10 minutes), 2 parts by mass of vinyltrimethoxy silane dissolved in acetone, and 0.2 parts by mass of dicumylperoxide were mixed. This mixture was extruded in the form of a strandwith a single screw extruder at 230° C., and pellets of modifiedpolyethylene containing 1.5% by mass of vinyl silane were obtained.Then, 5 parts by mass of the high-density polyethylene blended with 2%by mass of dibutyltin dilaurate, relative to 100 parts by mass of thesepellets, were blended and fed into a first extruder, and the pellets ofthe resin composition obtained above in the same way as Example 1 werefed into a second extruder, and an adhesive resin (“Admer-NF408E”manufactured by Mitsui Chemicals, Inc.) was fed into a third extruder.Then, a multilayered pipe having an outer diameter of 20 mm wasextrusion-molded with a three-material, three-layered circular die, andwas then immediately cooled and solidified using a cooling water bathwith temperature adjusted to 40° C. The layer configuration of themultilayered pipe included the resin composition layer as the outermostlayer, with the resin composition layer/adhesive resinlayer/high-density polyethylene layer=100 μm/100 μm/2000 μm. The pipethus obtained was inserted in a hot-air drier with a temperature of 140°C., and heat treatment was performed for 216 hours. The rate of increaseof dissolved oxygen was measured by the below-mentioned method using themultilayered pipe following heat treatment, and the rate of increase ofdissolved oxygen was measured to be 24 μg/L·hr.

(Method of Measuring the Rate of Increase of Dissolved Oxygen)

Water from which dissolved oxygen had been removed by use of a packedtower packed with metal tin was obtained. This water was circulated inthe obtained multilayered pipe at 70° C. The rate of increase ofdissolved oxygen in the circulating water was measured under anatmosphere of 20° C. and 65% RH. Herein, the rate of increase (μg/L·hr)means the rate of increase (μg/hr) of dissolved oxygen per liter ofwater circulating in the pipe. In other words, when the entire volume ofwater in the equipment system including the pipe is V (cc), the volumeof water in the pipe is v (cc), and the increased amount of thedissolved oxygen concentration in the water circulating in the systemper unit time is B μg/L·hr, then the rate of increase of dissolvedoxygen (A μg/L·hr) is A=B×(V/v).

Comparative Example 6

A three-material, three-layered, multilayered pipe was obtained in thesame manner as Example 20 except for the use of EVOH pellets (14)instead of pellets of the resin composition. The pipe thus obtained wasinserted in a hot-air drier with a temperature of 140° C., and heattreatment was performed for 216 hours. The rate of increase of dissolvedoxygen was measured by the above method using the multilayered pipeafter heat treatment, and the rate of increase of dissolved oxygen wasmeasured to be 90 μg/L·hr.

Example 21

100 parts by mass of a high-density polyethylene (“Yukaron Hard BX-50”manufactured by Mitsubishi Petrochemical Co., Ltd. having a density of0.952 g/cc and an MFR of 0.5 g/10 minutes), 2 parts by mass of vinyltrimethoxy silane and 0.2 parts by mass of dicumyl peroxide dissolved inacetone were mixed. This mixture was extruded in the form of a strandwith a single screw extruder at 230° C., and pellets of modifiedpolyethylene containing 1.5% by mass of vinyl silane were obtained.Then, 5 parts by mass of the high-density polyethylene blended with 2%by mass of dibutyltin dilaurate, relative to 100 parts by mass of thesepellets, were blended and fed into a first extruder, and the pellets ofthe resin composition obtained above in the same way as Example 1 werefed into a second extruder, and an adhesive resin (“Admer-NF408E”manufactured by Mitsui Chemicals, Inc.) was fed into a third extruder.Then, a multilayered pipe having an outer diameter of 20 mm wasextrusion-molded with a three-material, three-layered circular die, andwas then immediately cooled and solidified using a cooling water bathwith temperature adjusted to 40° C.

The layer configuration of the multilayered pipe included the resincomposition layer as the outermost layer, with the resin compositionlayer/adhesive resin layer/high-density polyethylene layer=100 μm/100μm/2000 μm. The multilayered pipe thus obtained was inserted in ahot-air drier with a temperature of 140° C., and heat treatment wasperformed for 10 minutes. Following this, the bending process wasperformed by bending the pipe by 90° along a stainless steel pipe withan outer diameter of 150 mm, and then fixing it for five minutes. Whenthe surface of the resin composition layer of the bent portion wasobserved, cracking due to distortion during the bending process was notseen. The rate of increase of dissolved oxygen was measured by the abovemethod for the multilayered pipe following the bending process, and therate of increase of dissolved oxygen was measured to be 24 μg/L·hr.

Reference Example 1

A multilayered pipe was obtained in the same manner as in Example 21except that the temperature of the cooling water bath through which themultilayered pipe passes immediately after extrusion-molding was changedto 5° C. The bending process was performed in the same manner as inExample 21 for the multilayered pipe thus obtained, and when the surfaceof the resin composition layer of the bent portion was observed, veryfew minute cracks were seen due to distortion during the bendingprocess. The rate of increase of dissolved oxygen was measured by theabove method for the multilayered pipe following the bending process,and the rate of increase of dissolved oxygen was measured to be 32μg/L·hr.

Reference Example 2

A multilayered pipe was obtained in the same manner as in Example 21except that the temperature of the cooling water bath through which themultilayered pipe passes immediately after extrusion-molding was changedto 85° C. The bending process was performed in the same manner as inExample 21 for the multilayered pipe thus obtained, and when the surfaceof the resin composition layer of the bent portion was observed, veryfew minute cracks were seen due to distortion during the bendingprocess. The rate of increase of dissolved oxygen was measured by theabove method for the multilayered pipe following the bending process,and the rate of increase of dissolved oxygen was measured to be 36μg/L·hr.

Comparative Example 7

A three-material, three-layered, multilayered pipe was obtained in thesame manner as Example 21 except for the use of EVOH pellets (14)instead of pellets of the resin composition. The bending process wasperformed in the same manner as in Example 21 for the multilayered pipethus obtained, and when the surface of the resin composition layer ofthe bent portion was observed, several minute cracks were seen due todistortion during the bending process. The rate of increase of dissolvedoxygen was measured by the above method for the multilayered pipefollowing the bending process, and the rate of increase of dissolvedoxygen was measured to be 76 μg/L·hr.

Example 22

The aforementioned high-density polyethylene was fed into a firstextruder, the pellets of the resin composition obtained above in thesame way as Example 1 were fed into a second extruder, and an adhesiveresin (“Admer-NF408E” manufactured by Mitsui Chemicals, Inc.) was fedinto a third extruder. Then, an outer-layer pipe having an outerdiameter of 77 mm was extrusion-molded with a three-material,three-layered circular die, and was then immediately cooled andsolidified using a cooling water bath with temperature adjusted to 40°C.

The layer configuration of the outer-layer pipe included the resincomposition layer as the innermost layer, with the resin compositionlayer/adhesive resin layer/high-density polyethylene layer=100 μm/100μm/2000 μm.

A steel pipe with an outer diameter of 20 mm was inserted inside theouter-layer pipe as the inner pipe, and fixed with a spacer. In thespace between the outer-layer pipe and the inner pipe, a mixture of 130parts by mass of a polyol composition and 115 parts by mass ofpolymethylene polyphenyl polyisocyanate (Crude MDI) (Millionate MR-200manufactured by Nippon Polyurethane Industry Co. Ltd.) was filled. Here,the polyol composition was prepared by mixing 3 parts by mass of asilicone foaming stabilizer (“SF2937” manufactured by Dow Corning TorayCo., Ltd.), 11 parts by mass of cyclopentane as the blowing agent, 1part by mass of triethylene diamine as an amine urethane catalyst, 8parts by mass of 1,2-butylene oxide, 0.3 parts by mass of zinc chlorideas a carbon dioxide fixation catalyst and 5.7 parts by mass oftetrabutylammonium bromide in 100 parts by mass of a polyol (SPINODOLRD-4011P manufactured by DIC Corporation). Next, after heating themixture for 10 minutes at 45° C. and then hardening, foamed polyurethanewas formed by keeping for 24 hours under room temperature, and amultilayered pipe for district energy composed of an inner pipe, aninsulation foam layer covering the surrounding of the inner pipe, and anouter-layer pipe was prepared. After performing heat treatment of themultilayered pipe thus obtained for 150 days at 90° C., a weight of 3.0kg having a hemispherical tip with a diameter of 25 mm was dropped froma height of 2 m under −20° C. for the impact resistance test accordingto ISO3127:1994, and the occurrence of cracking was not observed.

Comparative Example 8

A three-material, three-layered outer-layer pipe was obtained in thesame manner as Example 22 except for the use of EVOH pellets (14)instead of pellets of the resin composition, and a multilayered pipe fordistrict energy composed of an inner pipe, an insulation foam coveringthe surrounding of the inner pipe, and an outer-layer pipe was prepared.After performing heat treatment of the multilayered pipe thus obtainedfor 150 days at 90° C., a weight of 3.0 kg having a hemispherical tipwith a diameter of 25 mm was dropped from a height of 2 m under −20° C.for impact resistance test according to ISO3127:1994, and theprogression of cracks was observed.

INDUSTRIAL APPLICABILITY

The multilayered pipe having a layer comprising the resin composition ofthe present invention has excellent gas barrier property, and inhibitsthe oxidative degeneration of EVOH in the resin composition. Therefore,even after use under high temperatures for a long period of time,cracking in the resin composition layer (EVOH layer) does not occureasily as a result of oxidative degeneration. By making use of suchcharacteristics, the multilayered pipe of the present invention ispreferably used as a hot water circulation pipe and an insulatedmultilayered pipe.

1. An insulated multilayered pipe, comprising an insulation foam layerand a layer comprising a resin composition comprising an ethylene-vinylalcohol copolymer (A) and, relative to 100 parts by mass of theethylene-vinyl alcohol copolymer (A), 0.001 to 5 parts by mass of anantioxidant (B), and 0.00001 to 0.3 parts by mass of a conjugatedpolyene compound (C) having a molecular weight of 1000 or less. 2-15.(canceled)
 16. The insulated multilayered pipe according to claim 1,wherein the resin composition comprises 0.00005 to 0.2 parts by mass ofthe conjugated polyene compound (C).
 17. The insulated multilayered pipeaccording to claim 16, wherein the resin composition comprises 0.0001 to0.15 parts by mass of the conjugated polyene compound (C).
 18. Theinsulated multilayered pipe according to claim 1, wherein the conjugatedpolyene compound (C) has a molecular weight of 500 or less.
 19. Theinsulated multilayered pipe according to claim 1, wherein the conjugatedpolyene compound (C) has seven or fewer carbon-carbon double bonds toconjugate.
 20. The insulated multilayered pipe according to claim 19,wherein the conjugated polyene compound (C) is at least one selectedfrom a group consisting of sorbic acid, sorbic acid salt, and myrcene.21. The insulated multilayered pipe according to claim 20, wherein theconjugated polyene compound (C) is sorbic acid, a salt thereof, or both.22. The insulated multilayered pipe according to claim 1, wherein theresin composition comprises 0.01 to 4 parts by mass of the antioxidant(B).
 23. The insulated multilayered pipe according to claim 1, whereinthe antioxidant (B) is a compound comprising a hindered amine group, acompound comprising a hindered phenol group, or both.
 24. The insulatedmultilayered pipe according to claim 1, wherein the conjugated polyenecompound (C) is sorbic acid salt, a salt thereof, or both, and theantioxidant (B) is a compound comprising a hindered amine group, acompound comprising a hindered phenol group, or both.
 25. The insulatedmultilayered pipe according to claim 24, comprising 0.0001 to 0.15 partsby mass of the conjugated polyene compound (C) and 0.01 to 4 parts bymass of the antioxidant (B).
 26. An insulated multilayered pipeaccording to claim 1, comprising an inner pipe, an insulation foamlayer, and the layer comprising the resin composition in a sequence froman inner side.
 27. An insulated multilayered pipe according to claim 1,comprising an inner pipe, an insulation foam layer covering thesurrounding of the inner pipe, and an outer-layer pipe, in a sequencefrom an inner side, wherein the outer-layer pipe comprises a laminatecomprising the layer comprising the resin composition.
 28. An insulatedmultilayered pipe according to claim 27, wherein the outer-layer pipecomprises a layer comprising a thermoplastic resin, a layer comprisingan adhesive resin, and the layer comprising the resin composition. 29.An insulated multilayered pipe according to claim 28, wherein theouter-layer pipe has three-layer configuration of T/Ad/E in which the Elayer is arranged inwards from the T layer, where T layer is the layercomprising the thermoplastic resin, Ad layer is the layer comprising anadhesive resin, and E layer is the layer comprising the resincomposition.
 30. A method for producing the insulated multilayered pipeaccording to claim 27, the method comprising inserting the inner pipeinside the outer-layer pipe, fixing the inner pipe with a spacer to forma double pipe, and then pouring a foam feedstock in a space between theinner pipe and the outer-layer pipe and hardening.
 31. The method forproducing the insulated multilayered pipe according to claim 30, whereinthe outer-layer pipe is molded by co-extrusion molding.
 32. The methodfor producing the insulated multilayered pipe according to claim 31,comprising molding the outer-layer pipe by extrusion molding followed bycooling with water having a temperature of 10 to 70° C. immediatelyafter the molding.
 33. The method for producing the insulatedmultilayered pipe according to claim 31, wherein the outer-layer pipe ismolded by co-extrusion molding.